(From a reader mail. Personally as I've said before I would not buy a WD Green drive for my Mac Pro internal use. I have however used them for some specific external case uses (such as my compact Ministack case where cool running, less fan noise, etc. was a primary factor). All my Mac Pro HD bays are full with 7200rpm drives.)

"How to set wdidle3 on WD Green HD's using a 2008 MacPro
Using the wdidle3 application to set the idle timeout to DISABLED helps prevent the heads from parking excessively on WD drives. A consumer drive is apparently only good for a guaranteed 300k head parkings. More than that and who knows.(FYI: This concern also came up in the past here regarding notebook drives - see our Feb 2009 article on Notebook HD Load Cycle Counts (from end users) - several reports there noted their drives had over 1 million load cycles, some over 1.5 million (reports also include Power on Hours) - info from Smart Utility for OS X. And over the years there's been general posts on using (in OS X) hdapm here, most recently on the page of WD 750GB/640GB Scorpio HDs in MBPs.)
Many systems have an issue with this function also (Tivo's won't boot)

In my MacPro I could constantly hear the drive's parking. In 36 hours I had almost 700 parking events per drive. This is low compared to some of the reports of 4 parkings per minute but still... Lower the better.

The only drawback I can see about disabling the function is power consumption increases slightly during normal day to day activity.

The problem is, (WD's utility) is a DOS only utility! In a mac-only residence, this can be a challenge to get working. So this is how I did it. I have ONLY done this on a 2008 Mac Pro. (Although it should work in other intel-based Macs and via bootcamp (vs VM) - but there can be issues with some boot CDs with some macs as noted in past posts here on SSD firmware updates for instance where there were issues with optical drive/interface support with some models. For instance although a 2008 Mac Pro owner updated his Seagate HD firmware OK using a bootCD (PATA optical drives in 2006-2008 Mac Pros), I later had a 2009 mac pro owner report he couldn't.) Your results may vary. (And as always, have a current backup of your data, I'd also have ES/drive sleep disabled and have the system attached to an UPS just in case.)

Install winrar: uncompress the wdidle3.zip file to a folder called wdidle3.
right click on the ultimate boot ISO and select extract files.... In the path type c:\ubcd411
(WARNING do not try to modify the ISO with a program like ISOMagic. I had made several coasters trying that method. This is the only method that worked for me)

Copy the folder wdidle3 folder to c:\ubcd411\dossapps

Now type the following at a command prompt

cd c:\ubcd411\tools\ubcd2iso

ubcd2iso c:\ubcd411 ubcd411.iso

You will now have an ISO located at c:\ubcd411 called ubcd411.iso. Copy to your mac and burn using disk utility, or burn via windows if you have software.

Now reboot using this CD (holding option as to boot a bootcamp partition) and you will see a Windows labeled CD at the boot manager screen. Boot off the CD.

Click enter when you see the prompt to press enter to boot. You will then be presented with a blue screen with menu items.

Select Dos/Linux boot Disks

Select Dos boot disks

Select OpenDos Boot disk V3.40 (If this dosnt work for you, experiment. FreeDos did NOT work for me)

The machine will appear to hang at "Supported version of int 13 extensions: EDD-3.0" for a min. Don't worry and give it some time. Do not mess with ANY of the options that are presented during boot process. (little white popups)

Once it is 100% booted, the last white screen (Very large white popup) will "Time out" or you can click ok and you will be presented with a command prompt.

type

cd t:\dosapps\wdidle3

wdidle3 /d

This will DISABLE all parking on ALL attached WD drives on your system (Via SATA of course). It will skip any Non WD drives.

You're done. Now reboot and watch your Load Cycle Count stay virtually static.
-Stacy
PS: If your drive supports wdtler (Not supported with the newest green drives like my WD20EARS) (that's the new 4k sector 'advanced format' model) you can also copy it to the dossapps and execute this as well.
PPS: Use a program like Smart utility 2.2 to monitor your load cycle count's.
(Here's Volitan's Smart Utility for OS X home page)
PPPS: This will not destroy the data on the drives. But, like everything use at your OWN RISK.
(And again, always have a current backup (or 2) regardless.)"